Power-factor indicator.



No. 767,764. PATENTED AUG. 16, 1904. L. T. ROBINSON. POWER FACTOR INDICATOR.

APPLICATION FILED NOV. 5, 1902.

N0 MODEL. 2 SHEETS-SHEET 1.

Fig. I.

Witnesses Irwentor.

I Lewis T. Robinson.

M W M-Q No. 767,764. PATENTED AUG. 16, 1904. L. T. ROBINSON.

POWER FACTOR INDICATOR.

- APPLICATION FILED NOV. 5, 1902.

N0 MODEL. 2 SHEETS-SHEET 2.

Witnesses Inventor.

g v Lewis T.Ro i son. fl m v I I L W No. 767,764. latented August 16, 1904.

UNITED STATES PATENT OEFIcE.

LEWIS T. ROBINSON, OF SCHENEOTADY, NEW YORK, ASSIGNOR TO GEN- ERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

POWER-FACTOR IN DICATOR.

SPECIFICATION forming part of Letters Patent No. 767,764, dated August 16, 1904.

Application filed November 5, 1902. Serial No. 130,152. (No model.)

To all whom it may concern spokes L serving to connect the ring 1 with Be it known that I, LEWIS T. ROBINSON, a the pivoted shaft. (Not shown.) 5 citizen of the United States, residing at Schen- Mounted in operative relation to the ring 1 ectady, county of Schenectady, State of New and separated from each other to a suitable 5 York, have invented certain new and useful extent are two motor elements, each consist- Improvements in Power-Factor Indicators, of ing of a potential-coil and two current-coils which the following is a specification. similar to the motor elements of ordinary al- 55 My present invention relates to means for ternating current induction meters. The measuring or indicating the power factor of motor element (indicated generally at 5) conalternating-current circuits, and is embodied sists of a potential-coil 6 and two current-coils in a novel type of instrument in which a mov- 7 and 8, connected in series with each other. able element is acted upon inductively by a The potential-coil 6 is mounted upon one limb 60 plurality of motor elements the torques of of a magnetic core 9', between the jaws of which are adapted to vary relatively to each which the movable ring 1 is adapted to pass a. I 5 other in response to variation of power factor freely. The current-coils 7 and 8 are located and in which the movable element is so conbeneath the ring 1, one at one side of the postructed that it may turn into a position in tential-coil and one at the other. The other 5 which the torques of the motor elements balmotor element, 9, is similar to the motor ele- .ance each other. When there is no wattless ment 5 and consists of a potential-coil 10, current flowing, the movable element assumes mounted upon a core 11, and two cooperating a certain given or neutral position and is deseries-connected current-coils 12 13, the motor flected either to one side or the other from this element as a whole being arranged like the 7 position when wattless current does flow, the motor element 5, so that the pivoted or movdegree of deflection serving as a measure of able ring 1 may pass freely between the jaws of 2 5 the power factor and the direction of defiecthe core 11. In the particular arrangement tion as an indication as to whether lagging or shown the two motor elements 5 and 9 are arleadingcurrent is flowing. ranged diametrically opposite each other. 75 The novel features which I believe charac- As arranged in Fig. l, the instrument is terize my invention I have pointed out with shown connected up for measuring the power 3 particularity in the appended claims, while factor of a circuit feeding an induction-mothe invention itself I have described in detail I tor, (represented conventionallyat14,)the cirin the following specification, which is to be 1 cuit of the motor being shown connected so taken in connection with the accompanying across single-phase supply-mains 15; Ourdrawings, in which rent-coils 7 8 and 12 13 of the two motor ele- Figure 1 represents my invention as emments are therefore connected in series with bodied in an instrument for indicating the the induction-motor circuit. power factor of a single-phase alternating cur- One of the motor elements is made respon- 5 rent, while Fig. 2 shows an instrument arsive to the wattless current flowing in the alranged to indicate the power factor of a threeternating-current circuit to which the indi- 4 phase alternating current. cator maybe attached, while the other element In Fig. 1 the movable element of the indiis made responsive to the actual energy flowcator consists of a somewhat ring-shaped meming in said circuit. 9

her 1, having a portion thereof cut away, so To make one of the motor elements of the as to form two opposing prongs 2 3 of a someindicator responsive to wattless currents, the what tapered outline. Themovable member potential-coil is connected to the supply-mains is carried by a pivoted support in the same through a relatively large non-inductive remanner as the rotating member of an ordinary sistance. Either of the motor elements may alternating-current induction-meter, the light be thus connected; but, as shown in the drav ings, l have represented the potential-coil 6 of the motor element as thus arranged. it will be evident that when there is no wattless current flowing the current in the poten tial-coil 6 will be in phase with the current in the current-coils 7 and 8, under which conditions there will evidently be no torque exerted by the motor element (5 upon the movable elementl of the indicator. The potential- 1 coil 10 of the other motorelcment is, however.

connectedto the supply-mains through an inductance-coil 16, the purpose of which is to produce in the potential-circuit a current lagging as nearly as possible to ninety degrees behind the impressed electromotive force. As thus arranged, the motor element9 produces a maximum torque when the power factor is at or near unity and less torque as the amount of lagging current increases. The motor element 9 operates to turn the movable element of the meter until the prongs 2 and 3 of the movable element are brought around into proximity to the motor element. \Vhen there is no wattless current flowing, this turning action brings the prongs into substantially symmetrical relation with the motor element 9, one prong lying at one side of the potentialcoil and the other prong at the other side. The alternating field produced by the motor element 9 tends to repel each prong out of the field, with the result that the movable element turns until it assumes a position where the forces of deflection are balanced, this position being a symmetrical position, as shown in the drawings, when there is no torque produced by the motor element 6, a condition which exists when no lagging current is flowing in the circuit. If, however, a lagging current is flowing, such as would exist when the motor 14 is connected in circuit, the current in the current-coils 7 and 8 is no longer in phase with the electromotive force impressed upon the potential-coil 6, but lags behind the current in the potential-coil. The fluxes produced by the current-coils and the potentialcoil of the element 5 therefore give rise to a rotary field, which acting inductively upon the rotating member 1 turns the same about its axis of rotation in opposition to the torque exerted. by the motor element 9 upon one or the other of the prongs 2 3. As the angle of deflection of the movable member increases one of the prongs is moved more and more into and through the magnetic field of the motor element 9. The prongs of the movable member being tapered give rise to stronger and stronger induced or eddy currents, as one or the other of them is moved more and more against or in opposition to the field produced by the motor element 9. The turning of the motor element continues until the torque produced by the motor element is balanced by that produced by the other motor element, 9.

. The angle of deflection of the movable ele- 16, moving over a suitable scale 17, the deflection serving as a measure of the relation between the amounts of wattless current and energy current in the circuit, or, in other words, of the'power factor. The deflection of the instrument will be at one side of the zero position when the wattless current is a lagging current and at the other side when it is a leading current.

In Fig. 2 the indicator is shown applied to a three-phase alternating-current system for the purpose of measuring the power factor. The instrument is similar in construction to that already described in connection with Fig. 1, and its corresponding parts are therefore correspondingly designated. The two sets of current-coils 12 13 and 7 8 instead of being connected in series with each other, as in Fig. 1, are connected one set in series with one of the three-phase mains-such, for example, as the main 18and the other set in series with another three-phase main, 19. The potential-circuit of the motor element 9 is connected across one pair of three-phase mains 19 20 and the potential-circuit of the other motor element, 5, across the mains 18 20. In each potential-circuit an inductance-coil is connected so as to cause the current to lag as nearly ninety degrees as possible, the inductance-coils being indicated at 21 and 22. WVith change of power factor of the system the torques produced by the motor elements vary relatively to each other, thereby causing the movable elements to rotate into a position where the torques are again balanced. The torques become equalized by the shifting of the prongs of the movable element relatively to one of the motor elements in a manner already described in connection with Fig. 1. A pointer 16, carried by the movable element and movable over a scale 17, serves to indicate the magnitude of the quantity measured.

The three-phase mains 18 19 20 are represented as supplying current to an inductionmotor 23; but it is of course evident that the character of the load is immaterial so far as concerns my invention. Moreover, although I have shown my invention as applied to both single-phase and three-phase systems I do not wish to be limited thereto, since the invention is applicable to other alternating-current systems as well.

hat I claim as new, and desire to secure by Letters Patent of the United States, is-

1. The combination of a plurality of motor elements, and a movable element within the inductive influence of said motor elements and adapted by'shifting its position to vary the torque exerted thereon by one or more of said motor elements.

2. In an electrical instrument, the combination of a plurality of electromagnetic motor elements, and a movableelement within the inductive influence of said motor elements and constructed so as to present portions of varying conductivity to the inductive influence of one or more of said motor elements as it is moved relatively thereto.

3. In an electrical instrument, the combination of motor elements, a relatively movable element within the influence of said motor elements and constructed so that by shifting its position relatively to the motor elements it operates to produce a balance between the torques exerted thereon by the motor elements, and means for observing the relative motion of said relatively movable element.

4. In an electrical instrument, the combination of two motor elements, one responsive to the flow of wattless current in an alternatingcurrent system and the other to the flow of energy current in such system, and a member in operative relation to the motor elements and arranged so as to be movable into aposi tion whereinthe torques exerted thereon by the motor elements are in a condition of balance.

5. In an alternating-current instrument, the combination of a movable member the continuity of which is interrupted inthe direction of its movement, two motor elements each mounted to act inductively upon the movable element, means for rendering the torque produced by one of the motor elements responsive to the wattless current flowing in an alternating-current circuit, means for rendering the torque of the other motor element responsive to the energy current flowing in such circuit, and means for observing the deflections of the movable member corresponding to positions where the torques produced by the two motor elements are balanced.

6. In an electrical instrument, the combination of a movable member, two motor elements mounted each in inductive relation to the movable member and provided respectively with current and potential coils, means for causing one of the elements to exert a torque upon the movable member responsive to the Wattless current of an alternating-current system, and means for causing the other motor element to exert a torque upon the movable member responsive to the energy current of the system.

In witness whereof I have hereunto set my hand this 1st day of November, 1902.

LEWIS T. ROBINSON.

Witnesses:

BENJAMIN B. HULL, IVIARGARET E. VVooLLEY. 

